Kenneth E. Gibson

Development of post-fire crown damage mortality thresholds in ponderosa pine

Previous research has shown that crown scorch volume and crown consumption volume are the major predictors of post-fire mortality in ponderosa pine. In this study, we use piecewise logistic regression models of crown scorch data from 6633 trees in five wildfires from the Intermountain West to locate a mortality threshold at 88% scorch by volume for trees with no crown consumption. For trees with 440% crown consumption volume, linear regression indicates 485% mortality, but for trees with crown consumption volume o40%, there is a statistically significant, linear relationship between increasing crown scorch and increasing probability of mortality. Analysis of an independent 600þ tree dataset from Colorado produced similar results and supports the analysis approach. Crown scorch volume (485%), crown consumption volume (440%), and crown consumption between 5 and 40% combined with crown scorch volume 450% mortality thresholds could be incorporated into post-fire marking guidelines for forest management goals. Additionalkeywords: crown consumption,crown scorch,logisticregression, markingguidelines,piecewise regression, Pinus ponderosa, statistical models, wildfire.